Note the special symbol like a box in the angle. If you see this, it is a right angle. The 90° is rarely written in. If you see the box in the corner, you are being told it is a right angle.
The obtuse angle is the smaller angle.
It is more than 90° and less than 180°.
A straight angle changes the direction to point the opposite way.
Sometimes people say "You did a complete 180 on that!" ... meaning you completely changed your mind, idea or direction.
A Reflex Angle is more than 180° but less than 360°